Colleagues
Consider:smokers <- c( 83, 90, 129, 70 )
patients <- c( 86, 93, 136, 82 )
prop.test(smokers, patients)
4-sample test for equality of proportions
without continuity correction
data: smokers out of patients
X-squared = 12.6, df = 3, p-value = 0.005585
alternative hypothesis: two.sided
sample estimates:
prop 1 prop 2 prop 3 prop 4
0.9651163 0.9677419 0.9485294 0.8536585
Now:prop.trend.test(smokers, patients) Chi-squared Test for Trend in
Proportions
data: smokers out of patients ,
using scores: 1 2 3 4
X-squared = 8.2249, df = 1, p-value = 0.004132
How can one determine the direction of the trend?
Thomas Subia
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